1. Field of the Invention
The invention relates to the binding of sheet groups, and more particularly to the binding of perforated sheets by plastic or metal binding elements. The invention is particularly concerned with the binding of items such as calendars.
2. Description of the Prior Art
Present methods of binding sheet groups of this type include spiral and zig-zag wire binders as well as plastic combs which have curved projecting fingers and a spine. A drawback of spiral binders is that the sheets will be offset sideways when they are folded back, detracting from the appearance of some calendars. In addition, some persons object to the possibility of exposed wire ends which could scratch. Plastic combs are expensive since they must be preformed, and insertion of this type as well as zig-zag binders is relatively slow. Automatic insertion is sometimes unavailable for the comb type of binder, and the spine of the comb prevents complete flat foldback of the sheets, desirable in a calendar and similar sheet groups.
A search on the subject matter of this invention revealed the following United States patents:
Spinner U.S. Pat. No. 2,435,561 showing a group of binder rings performed by rolling a sheet around a mandrel after resting it on a heated table.
Rose U.S. Pat. No. 2,423,817 showing metal T-members which are inserted and then bent.
Nadherny U.S. Pat. No. 3,038,181 showing ribbons of ring-forming plastic which are passed vertically through a guide after which the stack is moved horizontally to force the strips into an anvil, with an electrode welding their overlapping edges.
Byland U.S. Pat. No. 3,124,818 using plastic ribbons which are sealed.
The following patents which show different methods of binding stacks:
York U.S. Pat. No. 868,746
Seaborn U.S. Pat. No. 3,555,587
Staats et al. U.S. Pat. No. 3,576,690
Cooley U.S. Pat. No. 3,763,513
Staats et al. U.S. Pat. No. 3,839,759
Douvry Australian Pat. No. 11,341/33
For reasons which will become apparent, none of these patents are believed to anticipate or teach the present invention.